Many core and metro networks have already migrated to fibre optics. Fibre optics are also entering the access network arena, reaching the neighbour-hood, the premises, the business and the home. New packet technologies create new applications, driving demand for bandwidth and higher QoS (Quality of Service), including high network availability.
All this traffic is enabled by multiple optical resources, which are gathered together to construct a transport network. These resources include fibres, passive optical elements, CPE equipment (routers, switches, line cards), network equipment (transponders, DWDM multiplexers, optical amplifiers, regenerators), and more. However, it is enough for one of these heterogeneous resources to fail in order to bring the network down, as in the case of fibre cuts during road construction or equipment failure. Backup resources which can quickly take over upon such a failure are essential to guarantee high network availability. This is where optical channel protection comes into play to provide for the contingency of provisioning alternate paths for optical communication traffic data in the event the main data path becomes inoperable.
Protection of traffic in optical networks can generally be classified under two types. The first type of protection being a concept of line protection is a so-called Optical Multiplex Section (OMS) protection used preferably in a multi-channel multi-section ring networks. The ring network is formed by at least two concentric optical fibre rings capable of carrying data traffic in two opposite directions (clockwise and counter-clockwise) between network elements NE in the ring. The two concentric fibre rings usually serve as a main route and a protection route for all optical channels of the network, although sometimes the main and the protection routes are arranged within the same fibre. The OMS protection ensures in case of a fault of the traffic via a multiplex section on the main route and a protection route (say in a section between two specific network elements, that may include multiple optical channels), the protection route that can be used to redirect the required data traffic from the main route, and thus bring the traffic to its destination network element using the opposite direction. In this case, the redirected traffic must pass a longer distance than it would pass via the main route. The OMS protection is usually utilized in SDH and SONET, where it is respectively named MSSPRING (Multiplex Section Shared Protection Ring) and BLSR (Bi-Directional Line Shared Protection).
The second known type of traffic protection in optical networks is a so-called OCH protection (Optical Channel Protection). The OCH protection is intended for protecting a specific optical channel and by default can be implemented by providing simultaneous transmission of data traffic of that specific optical channel along both the main route and the protection route. In case of a fault in one of the routes, the other will safely bring the traffic to its destination point.
U.S. Pat. No. 7,840,133 B2 provides a technique for carrying out protection of data traffic in a multi-channel multi-section optical communications network by simultaneously using Optical Multiplexed Section (OMS) protection and Optical Channel (OCH) protection. The technique comprises selection of a working optical signal in an OCH protected optical channel, in case of a fault in a section of the network, by relying on an indication associated with OMS switching functionality that is required to overcome the mentioned fault.
US 2002/0180957 A1 discloses a hub structure for use in an optical network, the optical network comprising a ring structure carrying a bidirectional optical data signal and a plurality of hub structures arranged in-line within the ring structure, the optical data signal comprising primary and secondary path transmission signals having opposing transmission directions on the ring structure, the hub structure comprising a drop unit arranged, in a normal state, to drop and through connect a secondary receive path signal for further processing at the hub structure.
Thus far there has yet to be disclosed an apparatus and method of cost effective optical channel protection for optical communication networks that enables switching between a primary data transmission path that serves as a main data transmission path and a secondary data transmission path that serves as an auxiliary data transmission path in the event the primary data transmission path experiences a fault.